Core structure



April l, 1958 G. H. ALLEN 2,829,356

CORE STRUCTURE Filed April 24, v195e 4 JZ 23 28 3/ 4/ ,ff/ 9! 2 24 l i?INVENTOR.

. 45 I @ff/4L@ All/V @URE STRUCTURE Gerald H. Allen, Kalamazoo Township,Kalamazoo County, Mich., assigner to Allen Electric and EquipmentCompany, Kalamazoo, Mich., a corporation `of Michigan Application April24, 1956, Serial No. 580,235

l Claim. (Cl. 336-212.)

This invention relates to transformerconstruction and relatesparticularly to a multi-leaved core construction having numerousstructural assembly and operatingadvantages.

ln the manufacture of transformers having a laminated core, it has longbeen common to fabricate said cores vby punching the individual laminaefrom sheet material,

applying the transformer windings to a portion of the stacked laminae orcore parts, and then to assemble the core in operating relationshipwithin an enclircling frame member. For purposes of economy of bothmaterial and labor, there has long been developed several types oftransformers, of which one is shown by U. S. Patent No. 1,297,161,wherein the core and frame members are stamped from a single sheet ofmetal and the core pieces are arranged in an H-shape so that the windingmay be applied around the web of the H and beheld in place by thefianges thereof.

ln studing the design of this general `type of transformer, l have foundthat a number of important features have apparently been overlooked inprevious designs of this character. These features, while not allunusual by themselves, when taken together in the overall patternhereinafter discussed further, result in a transformer havingunexpectedly desirable properties. Particularly, since these featuresoften point in .conliicting directions, insofar as their functionalresults arecon cerned, l have discovered a point at which theycan -bebalanced with excellent results.

Particularly, it is desirable to have the line of discontinuity betweenthe core structure and the surrounding frame structure as long aspossible in order to minimize the flux intensity at any point at whichlinx lines pass vfrom .one member across the line of discontinuity tothe other member, whereby reluctance losses arerminimized.

Further, it is desired to have the anges on each side of the web orcross bar of the above mentioned core pieces long enough to receive thefull amount of the winding and protect it to a maximum extent, yetwithout extending such flanges beyond the point at which they arefunctionally advantageous. On the other hand, too much extension of saidiianges will result in unreasonable weakening of them and will presentboth stamping and assembly problems.

Accordingly, a principal object of the invention has been to provide atransformer construction of maximum magnetic eiciency with minimum ofmechanical fabrication and assembly problems.

A further object of the invention has been to provide a transformer, asaforesaid, in which the flux density at all points where lines of linxpass a line of discontinuity between portions of metal carrying suchflux is reduced to a minimum, but wherein said reduction remainsconsistent with easy mechanical fabrication and assembly.

A further object of the invention has been to provide a transformer, asaforesaid, whose general arrangement and construction is sufficientlylike presently known trans- 2,829,356 AvE'attentati Apr. 1, i958 formersthat it will be readily accepted by the market and Vwill be readilyaccepted and understood by manufactoring, utilizing and servicepersonnel.

A further object of the invention has been to provide a transformer, asaforesaid, which can be manufactured at a very low cost.

A further obiect of the invention has been to provide .zi-transformer,as aforesaid, so designed that dimensional variations between the partsoccurring during the fabrication thereof, such as variations occurringby the wearing of the punchingdies, will be either self-compensatingorwill be self-absorbing and will therefore not interfere with theassembly and accurate inter-fitting of the parts.

A further object of the invention has been to provide a transformer, asaforesaid, wherein the winding can be rapidly applied thereto and willbe adequately protected when in operating position.

A further object of the invention has been to provide a transformer, asaforesaid, which will be sturdy and capable of long and reliable use.

Other objects and purposes of the invention will be apparent to personsacquainted with devices of this general `type upon reading the followingdisclosure and `inspecting the accompanyingy drawings.

in the drawings:

Figure l is an oblique view of a transformer embodying the, invention.

Figure 2 is a sectional view taken along the linell-Il of Figure l.

Figure 3 is an enlarged lfragment of Figure 2.

Figure 4 is a fragment of FigureZ showing an alternate construction.

General description Theinvention provides a transformer itl (Figures land 2) vhaving a core 9 comprised of an outer -frame portion irland agenerally l-l-shaped inner portion l2.

Detailed construction VThe outer `portion il of the transformer core 9is comprised of a plurality of preferably identical, laminated plates 16which are generally rectangular in shape. The

4plates 16 are assembled or stacked to form a unitary structure and areheld together'by Yelongated fasteners iigf adjacent y.to the fourcorners thereof. ,The fasteners in this particular embodiment are tubesof suitable length which extend through openings i5 in said plates andwhich are flared at their ends to prevent dislodgement of the plates. Itis apparent that other types of fasteners suitable for this purpose maybe used, if desired. rthe plates lo are each provided with a centralopening i8 having iirst and second edges 2i) and 2i, respectively, whichare substantially straight, equal in length and parallel with the endedges of the plate lo. The opening 18 has third and fourth edges 22 and23, respectively. Each of the edges 22 and 23 has a concave, arcuateportion 24, which is preferably circular or elliptical in shape,comprising the major extent of the length thereof. The curvature of eachportion 2li is such that, if extended, it would intersect the adjacentends of the first and second edges 2li and 2li, respectively. However,at a point close to the respectively adjacent ends of the first andsecond edges, the radius of curvature of 0 portion 24 is progressivelyshortened in the region 26 until the curved edge intersects an imaginaryline connecting corresponding ends of the first and second edges 20 and21. The end portions Z7 of each of said edges 22 and 23 consist in thisparticular embodiment of straight segments lying along said imaginaryline. Said end portions may, however, be provided with any desiredshape.

The inner portion 12 of the transformer core consists of a plurality oflaminated, generally H-shaped plates 36'. The plates 35B are identicaland each have flanges 28 and 29 with convexly arcuate outer edges 31 and32 which conform to the arcuate, concave shape of portion 24 and region26 of the edges 22 and 23. In fact, the inner portion 12 may be stampedfrom the outer portion 11 to provide at least a part of the opening 13,thereby facilitating economical and speedy fabrication as well as toeffect, and maintain even through various stages of die wear, a snug titbetween said convex and concave edges. As a result of the H-shape of theplates 30, the edges 34 and 3S of the web 36 in each inner plate 3) arespaced from the corresponding, opposing edges 20 and 21, respectively,for receiving the winding 13 therebetween. Removal of the metal whichproduces this spacing is also accomplished during the stampingoperation. The plates 30 are held in their laminated assembly byfasteners 33, which are of any convenient nature, such as bolts.

The plates 16 and 3@ are provided with mating recesses 37 which define apassageway, if desired, for a stacking key 3S, which key may besubsequently aixed permanently in place, or removed, as desired. Thus,the plates 16 and 30 must be oriented properly before they can beassembled on the stacking key.

The flanges 28 and 29 of plates 30 are of sufficient length that theentirety of the transformer winding 13 can be received therebetween toprovide side support for the entire radial extent of that portion ofsaid winding which lies between said flanges. The winding 13 may, ifdesired, be covered by any suitable protective cover 40, such asvarnish. A pair of channel-shaped jackets 41, which are made ofinsulating material engage the said winding 13 on three sides and areprovided with an open fourth side facing the edges 21 and 22 of frameportion 11. The outer edges 45 and 46 of each of the jackets convergetoward each other to retain the winding 13 therewithin and engage theedges 20 and 21 of plates 16 to space the winding 13 from said edges andthereby maintain an air gap 47 therebetween., Said edges 45 and 46 arepreferably slightly wider than the width of the air gap 47 andsufliciently resilient both to maintain the desired spacing and toabsorb manufacturing varations between the parts. Alternatively, theedges 45 and 46 may be extended, if desired and as indicated at 45' and46 in Figure 4, to overlap each other and thereby provide positiveinsulation of the winding from the face 20 instead of the air gap 47.

The engagement of the edges 31 and 32 of the inner plates 30 with theedges 22 and 23, respectively, of the outer plates 16 provides lines andareas of discontinuity between the inner portion 12 and the outerportion 11 of the core 9. Since these areas are curved away from thecenter of the transformer core 9, they provide the least possible lluxintensity per unit of area while avoiding undesirable concentrations offlux in any given area. Also, the shape of the portions 11 and 12provides the maximum permissible area of discontinuity available in thistype of transformer which is commensurate with eicient manufacturingpractices.

Although a particular, preferred embodiment of the invention has beendisclosed above for illustrative purposes, it will be understood thatvariations thereof within the scope of such disclosure are fullycontemplated unless specifically stated to the contrary in the appendedclaim.

I claim:

A transformer construction of the laminated core type, including incombination: a plurality of core elements arranged in superposedrelationship, each of said elements including an external frame memberhaving a central opening therewithin, said central opening having firstand second parallel, substantially straight sides and third and fourthconcavely curved sides facing each other; a generally H-shaped innermember with the remote edges of the legs thereof being curved to titsnugly against said third and fourth sides of said frame member, saidlegs extending to points spaced a slight distance from said first andsecond sides; a pair of channel-shaped insulating members, the webs ofsaid channel-shaped members lying adjacent the respective edges of theweb of said inner member, said channel-shaped members opening towardsaid first and second sides, respectively, with the outer ends of thelegs thereof being curved toward each other and positioned against saidfirst and second sides; transformer winding means wrapped around thewebs of said inner member and said channel-shaped members, said windingmeans being of approximately the same depth as the depth of the legs ofthe inner member and lying within said channel-shaped members, saiddepth of said winding means being materially less than the depth of saidlegs of said channel-shaped members, whereby the outer ends of the legsof said channelshaped members maintain the outer edges of said windingmeans spaced from said first and second sides to provide an air gaptherebetween.

References Cited in the iile of this patent UNITED STATES PATENTS461,135 Stanley Oct. 13, 1891 1,260,743 Attila Mar. 26, 1918

